//137.只出现一次的数字II
class Solution {
    public int singleNumber(int[] nums) {
        int ret = 0;
        for(int i = 0;i < 32;i++){
            int sum = 0;
            for(int x : nums){
                if(((x >> i) & 1) ==1){
                    sum++;
                }
            }
            sum %= 3;
            if(sum == 1){
                ret |= 1 << i;
            }
        }
        return ret;
    }
}